Water leaking from a mine at Kakadu National Park in Australia contains uranium concentration 5,400 times more than the natural background level, the Australian Office of the Supervising Scientist (OSS) said.

The mine operator, however, said these figures, which call in to question practices at one of the world’s most regulated mining sites, could not be proven.

The environmental regulator OSS told the Senate estimates committee that Energy Resources of Australia’s (ERA) Ranger uranium mine has been experiencing 100,000l of water seepage every day from the tailings dam for several years.

Greens senator Scott Ludlam says the regulator says it will not be possible to renovate the site, in one of Australia’s most sensitive wildlife environments, according to ABC News.

“The uranium concentration in the billabong surrounding the mine are about three to five parts per billion,” Ludlam said.

“But the uranium in the processed water that is leaking from beneath the tailings dam is 27,000 parts per billion.

“So it’s roughly 5,500 times as much uranium in that water as there is the surrounding environment and that means the company has got a huge problem.”

Ludlam said proper water quality sampling would be required to know exactly what level of contamination is being dealt with at the site.

ERA rejected the report, however, and said it was still unclear what context the OSS figures were taken in.